Asphalt has a broad range of applications from roofing to paving. With the increasing costs of asphalt, bitumen, tar or mixtures thereof, it is becoming cheaper over the long term to modify such materials with relatively small amounts of polymers. This tends to improve the properties of asphalt, bitumen, tar and mixtures thereof at temperatures in excess of 135.degree. F. (e.g. estimated road temperature in Arizona on a hot day) and at temperatures below about 40.degree. F. Generally, the high temperature rheology of the asphalt, bitumen, tar or a mixture thereof is improved (decreased flow) and the ductility of such materials at lower temperatures is also improved by polymer modification. As a result of the high cost of roofing and paving it is becoming economically advantageous to extend the life of products made with such material by modifying them with various polymers. While a premium price may be charged for polymer modified asphalt, bitumen, tar or a mixture thereof, it is extremely difficult to analyze the modified material to determine the presence and quantity of polymer. This has lead to the adoption of various indirect tests such as ductility (elongation tests) penetration tests, and torsional recovery tests (such as the test used by the California Highways Dept.--CAL 332). Unfortunately, this indirect test is prone to vary depending on the type and grade of asphalt, bitumen, tar or a mixture thereof which is used as a base. Thus, a polymer modified asphalt, bitumen, tar or mixture thereof may behave as if it is not polymer modified and a non-modified ashpalt, bitumen, coal tar or a mixture thereof may behave as if it is modified. This makes it extremely difficult for manufacturers and customers to provide quality control. To the best of applicants' knowledge there is no simple test to directly measure the polymer content in polymer modified asphalt, bitumen, tar or a mixture thereof.
There are a number of patents relating to various designs of gel permeation chromatographs (GPC's) such as U.S. Pat. No. 4,728,344 issued Mar. 1, 1988 assigned to Philips Petroleum which discloses a heated GPC. However, the Patent does not suggest using such a device to detect and quantify the polymer in polymer modified asphalt, bitumen, tar or a mixture thereof.
U.S. Pat. No. 3,719,084 issued Mar. 6, 1978, assigned to McDonnell Douglas discloses the use of a gas chromatograph to separate and/or identify complex mixtures of organic materials containing 1 to 20 carbon atoms. The polymers used to modify asphalt bitumen, tar and mixtures thereof contain more than 20 carbon atoms.
Commercially available columns for this application of gel permeation chromatography are STYRAGEL(Trademark--styrene-divinyl benzene gel) typically having a pore size from about 500 to 10,000 A. Such columns tend to plug if used to analyze polymer modified asphalt, bitumen, tar or a mixture thereof. Controlled pore glass is known but its suggested uses include separating protein molecules, viruses, cell components, and polymers having a molecular weight from 10.sup.3 to 10.sup.10. It has not been proposed to use such columns to separate polymers from asphalt, bitumen, tar or a mixture thereof.